Liquid cooling system for rotary internal combustion engine

ABSTRACT

The improved liquid cooling system is for a rotary internal combustion engine having a substantially trochoidal shaped housing cavity in which a rotor planetates, the engine being so constructed and disposed that the area of highest heat flux extends vertically along one side of the engine and substantially parallel to the major axis of the housing cavity. The cooling system comprises coolant inlet means and coolant outlet means disposed in the housing respectively below and above the minor axis of the housing cavity and a plurality of parallel passages in the housing adjacent the area of highest heat flux and extending substantially parallel to the longitudinal axis of the mainshaft, which passages are interconnected end-to-end for providing serial flow of coolant through successive passages from the inlet means to the outlet means so that flow of coolant is promoted by convection.

United States Patent [I91 Loyd, Jr. et al.

l l LIQUID COOLING SYSTEM FOR ROTARY INTERNAL COMBUSTION ENGINE [75] Inventors: Robert W. Loyd, .Ir., Wyckoff;

Charles Lombaerde, Ridgewood, both of NJ.

[73] Assignee: Curtiss-Wright Corporation,

Wood-Ridge, NJ.

221 Filed: Mar. 4, 1974 [21] Appl. No; 447,916

[ July 22, 1975 Primary Examiner-.lohn J. Vrablik Attorney, Agent, or Firm-Arthur Frederick; Victor D. Behn [57] ABSTRACT The improved liquid cooling system is for a rotary internal combustion engine having a substantially trochoidal shaped housing cavity in which a rotor planetates, the engine being so constructed and disposed that the area of highest heat flux extends vertically along one side of the engine and substantially parallel to the major axis of the housing cavity, The cooling system comprises coolant inlet means and coolant outlet means disposed in the housing respectively below and above the minor axis of the housing cavity and a plurality of parallel passages in the housing adjacent the area of highest heat flux and extending substan' tially parallel to the longitudinal axis of the mainshaft, which passages are interconnected end-to-end for providing serial flow of coolant through successive passages from the inlet means to the outlet means so that flow of coolant is promoted by convection.

4 Claims, 2 Drawing Figures LIQUID COOLING SYSTEM FOR ROTARY INTERNAL COMBUSTION ENGINE The invention relates to liquid cooling systems for rotary internal combustion engines and, more particularly, liquid cooling systems for the housing of the Wankel type rotary internal combustion engine.

In liquid cooling systems for the housing assembly of rotary internal combustion engines of the Wankel type, such as disclosed in the United States Patent to Wankel et al., No. 2,988,065, it is common practice to provide in the housing cooling flow passages extending substantially parallel to the axis of the mainshaft and header chambers in the housing end walls constructed and arranged to provide end-to-end interconnection of the passages and thereby provide serial flow of liquid through those passages. These conventional cooling systems are exemplified in the US. Patents to Lechler et al., 3,69l,999; Steinwart, No. 3,743,452; Turner, No. 3,289,647; Jones, No. 3,572,984 and Bentele et al.. No. 3,007,460. It is well recognized that heat transfer to a liquid at a specified temperature increases with an increase in the velocity of that liquid and, therefore, it is desirable in the aforesaid cooling systems to provide a high heat transfer rate and to accomplish this high heat transfer by circulation of liquid at high velocity. Thus, cooling systems constructed to provide flow of a relatively small quantity ofliquid at relatively high velocity in a rotary engine would require a thermostat and radiator of a size no larger than is required in the cooling system of a conventional reciprocating internal combustion engine of comparable size. To achieve this high velocity, the present invention contemplates a cooling system in which flow is promoted by convection, which also assists in carrying out of the cooling passageways entrained bubbles of gas and water vapor.

Accordingly. it is an object of this invention to provide a cooling system for the housing of a rotary internal combustion engine which efficiently effects transfer of heat from the housing to the liquid coolant.

Another object of the present invention is to provide a cooling system for the housing of a rotary internal combustion engine wherein flow of coolant is promoted by convection.

A further object of this invention is to provide a cool ing system for the housing of a rotary internal combustion engine wherein entrapment of gas and vapor is minimized.

SUMMARY Now, therefore. the present invention contemplates, a novel cooling system in a rotary internal combustion engine of the Wankel type having a multi-lobe housing cavity wherein combustion occurs in the area adjacent one of the junctures of the lobes and wherein the normal operative position of the engine is such that the area of highest heat flux on the housing extends substantially vertically of a horizontal plane. The cooling system for the housing of such engine comprises a plurality of first cooling passageways or passes in the housing adjacent the area of highest heat flux and extending substantially parallel to the longitudinal axis of the mainshaft of the engine and with header chambers in the housing end walls arranged to provide end-to-end connection of the first cooling passageways so that coolant will serially flow through successive first cooling passageways. The cooling system also calls for a coolant outlet port at the top of the housing and a coolant inlet port in the housing in the lower portion of the housing, the inlet port and outlet ports being in communication with said first cooling passageways to respectively pass coolant into and from the cooling passageways. The inlet port, outlet port and header chambers coact to provide for coolant flow through the cooling passageways successively upwardly past the area of highest heat flux whereby movement of coolant through the passageways from the inlet port to the outlet port is promoted by convection. The cooling system may also comprise a by-pass port means in the housing through which a relatively small amount, as for example 10 percent of the total amount of coolant flowing through the inlet port, is diverted into second cooling passageways or passes disposed in the housing adjacent the area of lowest heat flux and in communication with the outlet port to discharge heated coolant into the latter.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood from the following description when considered in connection with the accompanying drawings in which:

FIG. I is an exploded isometric view of the housing of a multirotor rotary internal combustion engine having a cooling system according to this invention, and

FIG. 2 is a schematic drawing of the end view of the engine of FIG. I showing the relationship of the major and minor axes of the housing cavities to a horizontal plane and the heat flux (Q/A) to which the housing is subjected during engine operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT Now referring to the drawings and more specifically to FIG. I, the reference number 10 generally refers to the housing of a rotary internal combustion engine of the Wankel type which engine may be of the one rotor or multi-rotor type. For purposes of illustration only, the invention is shown in FIG. 1 as having application to a two rotor rotary internal combustion engine. The housing 10 comprises two trochoid housing sections I2 and 14 separated by an intermediate wall section I6 and two opposite end wall sections I8 and 20. These housing components or sections 12, I4, 16, I8 and 20 are suitably aligned by dowels (not shown) extending through aligned openings 22 and secured together into a unitary structure by tie bolts (not shown) which extend through aligned openings (not shown) in each of the housing componentsv In the assembled condition the housing has two substantially trochoidal shaped cavities 24 within which rotors (not shown) are supported for planetation on a mainshaft (not shown), the mainshaft extending through the opening 26 in intermediate wall section 16 and end wall sections I8 and 20. The housing sections 12 and 14 are each provided with an exhaust port 28 and an ignition means 30, such as a spark plug. The intermediate housing I6 has a fuel and air supply inlet 32 which is bifurcated and communicates with two intake ports 34 and 36 in the opposite faces 37 of the intermediate housing. The intake ports 34 and 36 function to pass fuel and air into the combustion chambers (not shown) which are defined by the rotors (not shown) and disposed in cavities 24. Obviously, the invention is not limited to the intake ports 34 and 36. It is within the purview of this invention that any suitable means may be employed to provide a combustible mixture in the combustion chambers.

As best shown in FIG. 2, the engine in its normal operative position is orientated relative to a horizontal plane H, such that each of the major axes X--X and the minor axes Y--Y are disposeed to extend respectively substantially vertically and horizontally relative to the plane H. Also, as is shown in FIG. 2, the relative positions of intake ports 34 and 36, exhaust ports 28 and ignition means 30 are such that combustion produces a heat flux Q/A of varying degree as represented by the broken line and its distance from outline of housing (the greater the distance the greater the degree of heat transferred to the housing) of the engine. As herein described and as shown in FIG. 2, the area of highest heat flux extends along one side of the engine housing 10 and substantially parallel to the major axes X--X of the housing cavities 24. In order to minimize thermal distortion of housing 10 as a result of the heat flux Q/A, it is necessary to provide a cooling system for the housing which compensates for this varying degree of heat flux Q/A and, therefore, in accordance with this invention. housing 10 is provided with a liquid cooling system as hereinafter described.

As shown in FIG. 1, the cooling system comprises an inlet port means 38 and an outlet port means 40 in end wall section 18 and a first coolant passageway means in housing 10 located adjacent to the area of highest heat flux to conduct a liquid coolant from inlet port means 38 to outlet port means 40 through the housing and thereby absorb heat from housing 10. The cooling system may also include a second coolant passageway means in the housing 10 located adjacent the area of lowest heat flux and through which a small portion of the liquid coolant flowing through inlet port 38 is directed to flow through the second coolant passageway means.

The liquid cooling system. more specifically, provides for disposing both inlet port means 38 and outlet port means 40 in end wall section 18 of housing 10. The inlet port means 38 is located in the housing at a point below minor axes Y--Y and adjacent to or in alignment with major axes X--X. The outlet port means 40 is located in the housing at a point above minor axes Y--Y and adjacent to or in alignment with major axes X--X. As shown, end wall section 18 is divided by a plurality of webs 42 into an inlet header chamber 44, an intermediate header chamber 46 and an outlet header chamber 48, the inlet port means 38 communicating with inlet chamber 44 to deliver liquid coolant to the latter. The end wall section 18 is also provided with passage 50 which communicates with inlet header chamber 44 to receive liquid coolant from the chamber. This passage 50 constitutes part of the first coolant passageway means and is in register with passage 52 of the adjacent housing section 12. The passages 50 and 52 are in register with passages 54, 56 and 58 in the respective intermediate housing section 16, housing section 14 and end wall section 20. The passages 50, 52, 54, 56 and 58 coact to provide a first pass of the plurality of parallel passes or passages of the first coolant passageway means. The passage 58 communicates with a return bend chamber or intermediate header chamber 60 formed in end wall by webs 62 and 64 to pass liquid coolant into the header chamber 60. The end wall section 20 has another passage 66 which communicates with header chamber 60 to receive liquid coolant for flow back toward end wall 18. The passage 66 lies in register with passages 68, 70, 72 and 74 of housing sections 14, 16, 12 and 18, respectively. which passages constitute a second pass of the plurality of parallel passes or passages of the first coolant passageway means. The passage 74 communicates with intermediate header chamber 46 to discharge liquid coolant into the latter. A third pass of the first coolant passageway means consists of registered passages 76, 78, 80, 82 and 84 in housing sections 18, 12, 16, 14 and 20, respectively. which pass communicates with intermediate header chamber 46 to receive coolant from the latter. The passage 84 in end wall section 20 communicates with a return bend chamber or intermediate header chamber 86 formed in end wall section 20. This header chamber 86 also communicates with a passage 88 in end wall section 20 to deliver liquid coolant to the latter. The passage 88 registers with similar registered passages 90, 92, 94 and 96 in the respective housing sections l4, 16, 12 and 18. These registered passages 88, 90, 92, 94 and 96 constitute a fourth pass of the plurality of parallel passages of the first coolant passageway means and function to pass heated liquid coolant into outlet header chamber 48 in end wall section 18, which chamber communicates with passage 96. From outlet header chamber 48 the heated liquid coolant passes into outlet port means which may be connected to a thermostat (not shown). radiator (not shown) and a pump (not shown) for cooling and recirculation to inlet port means 38. As is clearly evident from the foregoing description, liquid coolant is conducted from inlet port means 38 to outlet port means 40 back and forth between end wall sections 18 and 20 through a plurality of passages which are positioned to receive liquid coolant at successively higher temperature as the coolant absorbs heat from the housing, thereby utilizing convection to promote the flow of liquid coolant. Thus, the velocity of flow is at a desired rate to achieve a heat transfer rate without high quantative flow of liquid coolant and a relatively large pump (not shown), if employed, and the attendant increase in radiator and thermostat size.

The liquid coolant system may also provide a second coolant passageway means for flowing liquid coolant in the area adjacent the portion of the housing where heat flux Q/A is least. This low heat flux is generally located in the area of the fuel and air supply inlet 32 and exhaust ports 28 (see FIG. 2). Since the heat transfer requirements in the area of least heat flux is low, only a small quantity of liquid coolant is necessary to achieve the desired heat transfer. Therefore, in accordance with the present invention, a by-pass port means 98 is provided in web 62 of end wall section 20 to communicate header chamber with an adjacent header chamber 100 formed in end wall section 20 between web 62 and a web 102. The by-pass port means 98 is so sized that of the total flow of liquid coolant entering header chamber 60, only a small amount, as for example about 10 percent, is diverted into header chamber 100 through by-pass port means 98. From header chamber 100 the liquid coolant flows in a single pass to outlet header chamber 48, via registered passages 104, 106, 108, and 112 in housing sections 20,14, l6, l2 and 18, respectively. The liquid coolant then flows from outlet header chamber 48 together with the liquid coolant from the first coolant passageway means via outlet port means 40. This fluid flow through the second coolant passageway means may for particular engines effect a transfer of heat to the housing rather than from the housing in order to provide a housing having minimal thermal distortion.

It is believed now readily apparent that the present invention provides an efficient liquid cooling system for a rotary internal combustion engine in which flow velocity of the coolant through the engine housing is promoted by convection since flow thereof from the cool ant inlet to the coolant outlet is in the same direction that temperature of the coolant is increased. it is a system in which the provision of disposing liquid coolant inlet and outlet ports in the same end wall section, eliminates in a multi-rotor engine, liquid coolant inlet and outlet manifolds and provides simplified housing castings.

What is claimed is:

1. In a rotary internal combustion engine in which a rotor is eccentrically mounted on a mainshaft so that the rotor planetates within a multi-lobed, substantially trochoidal shaped cavity formed within the housing of the engine and which engine is disposed in its normal operative position with the major and minor axes of the cavity respectively extending substantially vertically and parallel to a horizontal plane and wherein combustion occurs in the area adjacent one of the lobe junctures so that the area of highest heat flux extends substantially along one side of the housing parallel to the major axis of said cavity, a cooling system for the housing of said engine comprising:

a. a plurality of first cooling passageways in the housing adjacent the area where the highest heat flux is produced and extending substantially parallel to the longitudinal axis of said mainshaft',

b. header means forming chambers in the housing at the opposite ends of said housing to connect said first cooling passageways together end-to-end to provide for series flow of coolant through each of said plurality of first cooling passageways from one end of the housing to the other and upwardly adjacent said area of highest heat flux;

c. inlet means in the housing at a point below the minor axis of the trochoidal cavity and adjacent the combustion exhaust gas discharge means to communicate said first cooling passageways to a source of coolant to supply the first cooling passageways with coolant;

d. outlet means in the housing at a point above the minor axis to communicate with said first cooling passageways and receive heated coolant from the latter;

e. second cooling passageways in the housing adjacent the area where the lowest heat flux is produced and extending substantially parallel to the longitudinal axis of the mainshaft and communicating with said outlet means; and

f. by-pass means downstream from said inlet means for passing a portion of the coolant passing through said first cooling passageways into said second cooling passageways.

2. The cooling system of claim 1 wherein said header means are opposite end walls, the end walls being constructed and arranged to define said header chambers.

3. The apparatus of claim 2 wherein said by-pass means is located in one of said end walls.

4. The apparatus of claim 2 wherein said by-pass means is a passageway having a flow area sized to pass only a small portion of the total quantity of coolant passing through said inlet means.

l l t l l 

1. In a rotary internal combustion engine in which a rotor is eccentrically mounted on a mainshaft so that the rotor planetates within a multi-lobed, substantially trochoidal shaped cavity formed within the housing of the engine and which engine is disposed in its normal operative position with the major and minor axes of the cavity respectively extending substantially vertically and parallel to a horizontal plane and wherein combustion occurs in the area adjacent one of the lobe junctures so that the area of highest heat flux extends substantially along one side of the housing parallel to the major axis of said cavity, a cooling system for the housing of said engine comprising: a. a plurality of first cooling passageways in the housing adjacent the area where the highest heat flux is produced and extending substantially parallel to the longitudinal axis of said mainshaft; b. header means forming chambers in the housing at the opposite ends of said housing to connect said first cooling passageways together end-to-end to provide for series flow of coolant through each of said plurality of first cooling passageways from one end of the housing to the other and upwardly adjacent said area of highest heat flux; c. inlet means in the housing at a point below the minor axis of the trochoidal cavity and adjacent the combustion exhaust gas discharge means to communicate said first cooling passageways to a source of coolant to supply the first cooling passageways with coolant; d. outlet means in the housing at a point above the minor axis to communicate with said first cooling passageways and receive heated coolant from the latter; e. second cooling passageways in the housing adjacent the area where the lowest heat flux is produced and extending substantially parallel to the longitudinal axis of the mainshaft and communicating with said outlet means; and f. by-pass means downstream from said inlet means for passing a portion of the coolant passing through said first cooling passageways into said second cooling passageways.
 2. The cooling system of claim 1 wherein said header means are opposite end walls, the end walls being constructed and arranged to define said header chambers.
 3. The apparatus of claim 2 wherein said by-pass means is located in one of said end walls.
 4. The apparatus of claim 2 wherein said by-pass means is a passageway having a flow area sized to pass only a small portion of the total quantity of coolant passing through said inlet means. 